Silicon pressure sensors used to measure pressure in various systems and devices are often subjected to over pressures that exceed the full scale pressure rating of the sensor. Typical silicon sensors employing a deflectable on chip diaphragm to measure pressure are capable withstanding an over pressure of three to four times full scale pressure. If this level of over pressure rating is exceeded, the diaphragm will rupture, causing the pressure sensor to fail. Many applications require over pressure capability that can handle over pressures of ten times full scale or higher.
Conventional silicon pressure sensors are often protected from over pressure failure by external over pressure protection mechanisms. Such mechanisms add significant cost, complexity, and size to the pressure sensor function.
In other approaches for sensor protection, a deflection stop under the silicon pressure sensing diaphragm is employed such that the deflection is stopped after two times to three times full scale over pressure. While this is effective for over pressures less than about five times full scale, above that level, the over pressure loads the outer edges of the diaphragm even though the center is supported so that a shear failure occurs along the outer edge of the diaphragm, resulting in diaphragm failure.